How does the dshwshr rinse agent get into the rinse?

Hi All
The wife is indicating its time to get a new dishwasher.
Dishes dont seem to be as clean as they used to be.
Ive read all the threads on the topic.
BUT, I have noticed that the rinse agent does not seem to ever need refilling, so , I figured it was plugged.....
I pulled the complete back of the door out, and there is a chamber that holds the liquid rinse agent, but , I can not figure out how that rinse agent is supposed to be injected into the rinse.... there are no apparent ways for the liquid to make it into the dishwasher ...
Has anyone taken one of these apart and do you know how the liquid is dispensed......

How old is the dishwasher? When you say things aren't getting clean are you referring to things like particles and such not rinsing off? Or are you seeing etching of clear glass?

The newer dishwashers (last decade or so) seem to have progressively better spray patterns and such. I had an old one that I replaced about 10 years ago after it got to where it wouldn't clean anything. It was probably a worn pump or something as I don't think the spray nozzles/arms were doing much by then. I've since moved several times and it seems that each newer on has been better.

There is some real art & science to getting an effective and even distribution. The spray nozzle angles seem to have been improved and the coverage is much more even. Loading it in a way that actually cleans the dishes is much simpler now.

I also have a Kenmore Elite Dishwasher and my jet dry dispenser doesn't work. I think the liquid is dispensed out the bottom. Mine has a couple of opening under the edge of the dispenser. Mine leaks. If you fill it then in 2 days it is empty and the light is on again. It runs down on the inside of the door and into the tub. Was told that I need the whole dispenser. Comes as one piece for mine--detergent & rinse aid dispenser together.
I just use mine without the rinse aid. The stainless steel tub will be wet sometimes even using heated dry but the dishes are dry, unless it is plastic bowls or cups. Try using the Cascade Complete detergent. This seems to do better for me but then I know people have different water. You can also buy the solid form of jet dry that hangs in the top rack. Cheaper than a new machine if it helps fix your problem...